As a large-size bottle, which is easy to handle, there is known a synthetic resin bottle with a handle, in which the handle has been previously injection-molded into a certain shape and is used as an insert, and in which the PET bottle is biaxially drawn and blow-molded. However, it is desired that the handle is made of the same PET as used in the bottle, rather than a polyethylene resin or a polypropylene resin, so that the bottles can be separated and disposed easily at the time of waste disposal.
As conventional art that can meet this demand, Japanese Patent Application (OPI) No. 1994-298253 discloses that the fitting portions of the handle coming in contact with the bottle are crystallized to a degree of crystallinity of 10% or more. This makes it possible for the handle to be made of PET just as the bottle is made of PET. When the PET handle is fitted, usually the bottle tends to be ruptured because slide gets worse, but the crystallization prevents the bottle from rupturing during the drawing and deformation.
However, in the above-described conventional art, a dedicated operation is required for the crystallization treatment (typically, thermo-crystallization treatment) of the fitting portion, which is a specified portion of the handle. A problem arose here that it takes more time and labor to mold a bottle.
When the fitting portions of the handle are heated for crystallization, it is necessary to control the heat precisely, without giving any adverse effect thermally on the nearby portions. In practice, therefore, this requires high technological expertise, thus causing a problem that the operation cannot be conducted easily.
A technical problem of this invention is to improve the low slide between bottle and handle made of the same PET. An object of this invention is to obtain a biaxially drawn, blow-molded PET bottle, in which the PET handle is firmly fitted to the bottle as the insert, merely by an ordinary biaxial drawing and blow molding process, without requiring any dedicated operation.
As the handles to be used with this type of synthetic resin bottles with a handle, there are another disclosed in Japanese patent No. 2998820 and Japanese Patent Application (OPI) No. 2001-328636, which is an improvement from the above patent. A lot of these handles are in common use because stable and firm fitting can be secured and because handling of the inserts is easy.
The handle disclosed in the Japanese Patent Application (OPI) No. 2001-328636 is as shown in FIG. 16 and FIGS. 24–27. The handle comprises a grip plate 11′ in a vertical strip shape, embedded projecting pieces 14′ disposed on the front end faces at the extended end of this grip plate 11′, a pair of engaging ridges 15′ in a vertical ridge shape disposed on the sides facing each other, a pair of embedded fitting portions K′ that serve as strong undercut fittings to the bottle 1′, a pair of fitting beams 12′ in a vertical rod shape, and a pair of connecting arms 12a′ in the curved rod shape, which connect between the pair of fitting beams 12′ at both the upper and lower ends of the grip plate 11′.
In the case of this handle 10′ shown in these drawings, a vertical projecting wall 5′ is held tight by the pair of fitting beams 12′ when the wall 5′ is formed at the bottom 4′ of the recession 3′ of the bottle 1′. Therefore, the handle 10′ is stably and firmly fitted to the bottle 1′.
The afore-mentioned bottle with a handle can be obtained when injection-molded PET perform P′ is blow-molded into the bottle 1′. At that time, the previously injection-molded PET handle 10′ is fitted to the bottom of the handle-fitting recession 3′ at the rear of the body 2′ of the bottle 1′ by means of simultaneous insert molding.
During the process of afore-mentioned insert molding, the heated and softened PET preform P′ is smoothly deformed as its shape follows the shapes of the embedded projecting pieces 14′ and the engaging ridges 15′, which are the inserts of the handle 10′ and are fitted firmly to the bottle 1′. High fitting strength between the handle 10′ and the bottle 1′ is obtained by allowing the PET bottle wall portion to get around smoothly and tightly the peripheries of the handle inserts.
However, in the field of alcoholic beverages, juices and other soft drinks, there has lately been an increasing need for larger containers. Even if the bottles have a larger capacity, the neck does not have a large diameter, but has the same diameter as that of small-size bottles in many cases. As a result, it is required that thick-wall preform is drawn at a high magnification and that the biaxial drawing and blow molding operation has to be conducted at a high air-blow pressure.
Therefore, when the PET preform is drawn, a strong force pushes a portion of the expanding bottle wall against the surfaces of the inserts of the handle 10′, i.e., the surfaces of the connecting arms 12a′, the fitting beams 12′, and the embedded projecting portions. At that time, the PET bottle gets abrasions on the clear bottle wall, especially at places near the connecting arms 12a′. The problem of resultant bad appearance of the bottle has to be solved.
Another technical problem of this invention is to prevent abrasions from occurring at the inserts during the biaxial drawing and blow molding operation under a high blowing pressure. Another object of this invention is to provide a synthetic resin bottle with a handle, which has high safety, easy handling ability, and good appearance even in the case of large-size bottles reaching a capacity of a few liters.